Xiaoli Lan

The value of dual time point 18F-FDG PET imaging for the differentiation between malignant and benign lesions

AIM To assess the clinical value of dual time point 2-[(18)F]-fluoro-2-deoxy-d-glucose positron emission tomography ((18)F-FDG PET) imaging for the differentiation between malignant and benign lesions. MATERIALS AND METHODS Ninety-six patients (28 patients with primary lung cancer, 18 patients with digestive system carcinoma, 13 patients with other malignant tumours, and 37 patients with benign lesions) underwent FDG-PET/CT at two time points: examination 1 at 45-55 min and examination 2 at 160+/-24 (150-180) min after the intravenous injection of 233+/-52 (185-370)MBq (18)F-FDG. Reconstructed images were evaluated qualitatively and quantitatively. The maximum standardized uptake values (SUVmax) of the lesions were calculated for both time points. An increase was considered to have occurred if the SUVs at examination 2 had increased by >10% as compared with those at the examination 1. RESULTS The lesions in 24 of 28 (86%) patients with primary lung cancer had an SUVmax > or = 2.5 at examination 1. Of these, SUVmax values increased in 23 patients, but had not changed in one patient, at examination 2. The lesions in the other four patients with primary lung tumour had SUVmax values between 1.5 and 2.5 at examination 1, which were considered as suspected positive, increased SUVmax values were observed in three of these patients at examination 2. The malignant lesions in 17 of 18 patients with digestive system carcinoma showed SUVmax values > or = 2.5 and only one patient had an SUVmax value < 1.5 at examination 1; all lesions showed an increase in SUVmax values at examination 2. In 13 patients with other malignant tumours, all lesions had SUVmax values > or = 2.5 at examination 1 and the SUVmax values were further increased at examination 2. Therefore, the malignant lesions in 54/59 (92%) of patients had SUVmax values > or = 2.5 at examination 1 and showed a further increase in SUVmax value at examination 2. Only 12 of 37 (32%) patients with benign lesions showed SUVmax values > or = 2.5 at examination 1 and nine patients with benign lesions had SUVmax values > or = 2.5 in examination 2. The sensitivity, specificity, accuracy, positive and negative predictive values for the early and delayed imaging were 91.5, 67.6, 82.3, 81.8, and 83.3%, and 98.3, 75.7, 89.6, 86.6, and 96.6%, respectively. CONCLUSION The results of the present study provide further evidence that dual time point (18)F-FDG PET imaging is an important noninvasive method for the differentiation of malignant and nonmalignant lesions.

Tyrosinase as a multifunctional reporter gene for Photoacoustic/MRI/PET triple modality molecular imaging

Development of reporter genes for multimodality molecular imaging is highly important. In contrast to the conventional strategies which have focused on fusing several reporter genes together to serve as multimodal reporters, human tyrosinase (TYR) – the key enzyme in melanin production – was evaluated in this study as a stand-alone reporter gene for in vitro and in vivo photoacoustic imaging (PAI), magnetic resonance imaging (MRI) and positron emission tomography (PET). Human breast cancer cells MCF-7 transfected with a plasmid that encodes TYR (named as MCF-7-TYR) and non-transfected MCF-7 cells were used as positive and negative controls, respectively. Melanin targeted N-(2-(diethylamino)ethyl)-18F-5-fluoropicolinamide was used as a PET reporter probe. In vivo PAI/MRI/PET imaging studies showed that MCF-7-TYR tumors achieved significant higher signals and tumor-to-background contrasts than those of MCF-7 tumor. Our study demonstrates that TYR gene can be utilized as a multifunctional reporter gene for PAI/MRI/PET both in vitro and in vivo.

Fluorine-18 fluorodeoxyglucose positron emission tomography-computed tomography in monitoring the response of breast cancer to neoadjuvant chemotherapy: a meta-analysis.

INTRODUCTION To evaluate the diagnostic performance of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in monitoring the response of breast cancers to neoadjuvant chemotherapy. METHODS Articles published in medical and oncologic journals between January 2000 and June 2012 were identified by systematic MEDLINE, Cochrane Database for Systematic Reviews, and EMBASE, and by manual searches of the references listed in original and review articles. Quality of the included studies was assessed by using the quality assessment of diagnosis accuracy studies score tool. Meta-DiSc statistical software was used to calculate the summary sensitivity and specificity, positive predictive and negative predictive values, and the summary receiver operating characteristics curve (SROC). RESULTS Fifteen studies with 745 patients were included in the study after meeting the inclusion criteria. The pooled sensitivity and specificity of FDG-PET or PET/CT were 80.5% (95% CI, 75.9%-84.5%) and 78.8% (95% CI, 74.1%-83.0%), respectively, and the positive predictive and negative predictive values were 79.8% and 79.5%, respectively. After 1 and 2 courses of chemotherapy, the pooled sensitivity and false-positive rate were 78.2% (95% CI, 73.8%-82.5%) and 11.2%, respectively; and 82.4% (95% CI, 77.4%-86.1%) and 19.3%, respectively. CONCLUSIONS Analysis of the findings suggests that FDG-PET has moderately high sensitivity and specificity in early detection of responders from nonresponders, and can be applied in the evaluation of breast cancer response to neoadjuvant chemotherapy in patients with breast cancer.

Theranostics of Malignant Melanoma with 64CuCl2

Human copper transporter 1 (CTR1) is overexpressed in a variety of cancers. This study aimed to evaluate the use of 64CuCl2 as a theranostic agent for PET and radionuclide therapy of malignant melanoma. Methods: CTR1 expression levels were detected by Western blot analysis of a group of tumor cell lines. Two melanoma cell lines (B16F10 and A375M) that highly expressed CTR1 were then selected to study the uptake and efflux of 64CuCl2. Mice bearing B16F10 or A375M tumors (n = 4 for each group) were subjected to 5 min of static whole-body PET scans at different time points after intravenous injection of 64CuCl2. Dynamic scans were also obtained for B16F10 tumor–bearing mice. All mice were sacrificed at 72 h after injection of 64CuCl2, and biodistribution studies were performed. Mice bearing B16F10 or A375M tumors were further subjected to 64CuCl2 radionuclide therapy. Specifically, when the tumor size reached 0.5–0.8 cm in diameter, tumor-bearing mice were systemically administered 64CuCl2 (˜74 MBq) or phosphate-buffered saline, and tumor sizes were monitored over the treatment period. Results: CTR1 was found to be overexpressed in the cancer cell lines tested at different levels, and high expression levels in melanoma cells and tissues were observed (melanotic B16F10 and amelanotic A375M). 64CuCl2 displayed high and specific uptake in B16F10 and A375M cells. In vivo 64CuCl2 PET imaging demonstrated that both B16F10 and A375M tumors were clearly visualized. Radionuclide treatment studies showed that the tumor growth in both the B16F10 and the A375M models under 64CuCl2 treatment were much slower than that of the control group. Conclusion: Both melanotic and amelanotic melanomas (B16F10 and A375M) tested were found to overexpress CTR1. The tumors can be successfully visualized by 64CuCl2 PET and further treated by 64CuCl2, highlighting the high potential of using 64CuCl2 as a theranostic agent for the management of melanoma.

The antiproliferative effects of somatostatin receptor subtype 2 in breast cancer cells.

AbstractAim:Somatostatin receptor subtype 2 (SSTR2) is the principal mediator of somatostatins (SST) antiproliferative effects on normal and cancer cells. Therefore, we investigated whether the enhanced expression of SSTR2 could inhibit the proliferation of tumor cells, and, if so, the mechanisms that might be involved.Methods:SSTR2 expression levels were determined by qRT-PCR in several tumor cell lines. Then, a plasmid pIRES2-EGFP-SSTR2 (pSIG) was constructed and stably transfected into MCF-7 cells (MCF-7/pSIG). After SSTR2 overexpression was identified by qRT-PCR, immunofluorescence staining and a receptor binding assay, the MCF-7/pSIG cells were analyzed by PI staining for apoptosis and cell cycle arrest was tested by flow cytometry for epidermal growth factor receptor (EGFR) expression. The EGF-stimulated proliferation of MCF-7 cells was assayed by MTT.Results:The human breast cancer cell line MCF-7 expresses a lower level of SSTR2, thereby partly accounting for the decreased response to SST. The overexpression of SSTR2 in MCF-7 cells resulted in apoptosis, cytostasis and G1/S cell cycle arrest. Furthermore, the expression of EGFR, together with EGF-stimulated proliferation, was markedly decreased in the MCF-7/pSIG cells.Conclusion:Enhanced SSTR2 expression played an antiproliferative role in MCF-7 cells through inducing apoptosis and G1/S cell cycle arrest, and also by decreasing EGFR expression, thereby counteracting the growth-stimulating effect of EGF. Our data seem to indicate that developing a new therapeutic agent capable of upregulating SSTR expression could potentially be a way to block tumor progression.

Prognostic predictive value of total lesion glycolysis from 18F-FDG PET/CT in post-surgical patients with epithelial ovarian cancer.

Purpose The aim of this study was to determine an optimal threshold method for the segmentation of malignant lesions from 18F-FDG PET/CT images and to evaluate the prognostic value of the total lesion glycolysis in post-surgical patients with epithelial ovarian cancer. Methods We retrospectively reviewed 47 patients with pathologically proven epithelial ovarian cancer who underwent 18F-FDG PET/CT imaging after surgery. The follow-up time was 26.6 ± 19.8 months (ranged from 4 to 89 months). For each patient, every lesion was segmented by 2 thresholds with 3D-area growing algorithm, standard uptake value (SUV) 2.5, and background method. The detection rates were compared. The optimal threshold method was then used to calculate whole-body metabolic tumor volume (WBMTV) and whole-body total lesion glycolysis (WBTLG). The prognostic significance of SUVmax, WBMTV, WBTLG, and other pathological variables for overall survival were assessed by Cox proportional hazards regression analysis and Kaplan-Meier survival analysis. Results A total of 142 metastatic lesions of 47 patients were confirmed by long-term clinical follow-up or pathological findings. The detection rates of the threshold SUV 2.5 and background methods were 37.32% (53/142) and 96.48% (137/142), respectively, which showed significant difference between the 2 methods (P < 0.005). In multivariate analysis, WBTLG, obtained from the background method, was an independent predictive factor associated with the prognosis (HR 1.043, 95% CI 1.01-1.078, P = 0.011), and none of the other factors had statistical association. Survival analysis also showed that the survival time was clearly shortened with WBTLG increasing (P < 0.001). Conclusions In this group of post-surgery patients with epithelial ovarian cancer, the background method could segment much more malignant lesions than SUV = 2.5 method, and WBTLG, obtained from this method, could be used as an independent prognostic factor.

Multimodality molecular imaging to monitor transplanted stem cells for the treatment of ischemic heart disease.

Purpose Non-invasive techniques to monitor the survival and migration of transplanted stem cells in real-time is crucial for the success of stem cell therapy. The aim of this study was to explore multimodality molecular imaging to monitor transplanted stem cells with a triple-fused reporter gene [TGF; herpes simplex virus type 1 thymidine kinase (HSV1-tk), enhanced green fluorescence protein (eGFP), and firefly luciferase (FLuc)] in acute myocardial infarction rat models. Methods Rat myocardial infarction was established by ligating the left anterior descending coronary artery. A recombinant adenovirus carrying TGF (Ad5-TGF) was constructed. After transfection with Ad5-TGF, 5×106 bone marrow mesenchymal stem cells (BMSCs) were transplanted into the anterior wall of the left ventricle (n = 14). Untransfected BMSCs were as controls (n = 8). MicroPET/CT, fluorescence and bioluminescence imaging were performed. Continuous images were obtained at day 2, 3 and 7 after transplantation with all three imaging modalities and additional images were performed with bioluminescence imaging until day 15 after transplantation. Results High signals in the heart area were observed using microPET/CT, fluorescence and bioluminescence imaging of infarcted rats injected with Ad5-TGF-transfected BMSCs, whereas no signals were observed in controls. Semi-quantitative analysis showed the gradual decrease of signals in all three imaging modalities with time. Immunohistochemistry assays confirmed the location of the TGF protein expression was the same as the site of stem cell-specific marker expression, suggesting that TGF tracked the stem cells in situ. Conclusions We demonstrated that TGF could be used as a reporter gene to monitor stem cells in a myocardial infarction model by multimodality molecular imaging.

A multimodality reporter gene for monitoring transplanted stem cells

INTRODUCTION The aim of this study is to explore the feasibility of a triple-fused reporter gene, termed TGF [herpes simplex virus type 1 thymidine kinase (HSV1-tk), enhanced green fluorescent protein (eGFP) and firefly luciferase (Fluc)], to monitor stem cells using multimodality molecular imaging. METHODS A recombinant adenovirus vector carrying the triple-fused reporter gene (Ad5-TGF) was constructed. Bone marrow mesenchymal stem cells (BMSCs) were transfected with different virus titers of Ad5-TGF [multiplicities of infection (MOIs) were 0, 50, 100, 150, 200 and 250]. The mRNA and protein expressions of HSV1-tk, eGFP and Fluc in the transfected BMSCs were evaluated using polymerase chain reaction and Western blot. After the transfection of the BMSCs with different virus titers of Ad5-TGF (MOIs were 25, 50, 75, 100 and 125), their uptake rates of (131)I-FIAU were measured. Whole-body fluorescence, bioluminescence and micro-positron emission tomography (PET) images were acquired 1 day after the transfected BMSCs were injected into the left forelimb of rats. RESULTS After the transfection with different titers of Ad5-TGF, the positive transfection rate reached a peak (70%) when the MOI was 100. HSV1-tk, eGFP and Fluc mRNA and protein were detected in the Ad5-TGF-transfected BMSCs, which implies their successful transfection and expression. The BMSCs uptake of (131)I-FIAU increased with the adenovirus titer and incubation time and reached a plateau (approximately 5.3%) after 3 h. Strong signals were observed in the injected left forearms in the fluorescence, bioluminescence and micro-PET images. CONCLUSIONS A triple-fused reporter gene, TGF, can be used as a multifunctional molecular probe for multimodality imaging.

99mTc-labeled SWL specific peptide for targeting EphA2 receptor

INTRODUCTION EphA2, one member of the Eph receptor family, is widely expressed in multiple aggressive cancers. SWL, a small peptide identified by phage display, has high binding affinity to EphA2, suggesting that it could be exploited for targeted molecular imaging. Therefore, a novel peptide-based probe, (99m)Tc-HYNIC-SWL, was developed and its potential to specifically target EphA2-positive tumors was investigated. METHODS The SWL peptide was labeled with hydrazinonicotinic acid (HYNIC), followed by (99m)Tc labeling. Immunofluorescence staining was carried out to detect the expression of EphA2 in A549 lung cancer cells and OCM-1 melanoma cells. Saturation binding experiments were performed by incubating A549 cells with increasing concentrations of radiolabeled peptide in vitro. To test the probe in vivo, nude mice bearing either A549 or OCM-1 derived tumors were established, injected with (99m)Tc-HYNIC-SWL, and subjected to SPECT imaging. Mice injected with excess unlabeled SWL were used as a specific control. Ex vivo γ-counting of dissected tissues from the mice was also performed to evaluate biodistribution. RESULTS Immunofluorescence staining showed that A549 cells intensively expressed EphA2, while OCM-1 cells had little expression. (99m)Tc-HYNIC-SWL displayed high binding affinity with A549 cells (KD=2.6±0.7nM). From the SPECT images and the results of the biodistribution study, significantly higher uptake of the tracer was seen in A549 tumors (1.44±0.12 %ID/g) than in OCM-1 tumors (0.43±0.20 %ID/g) at 1h after injection. Pre-injection with excess unlabeled peptide in A549-bearing nude mice, significantly reduced tumor uptake of the radiolabeled probe (0.58±0.20 %ID/g) was seen. These data suggest that (99m)Tc-HYNIC-SWL specifically targets EphA2 in tumors. CONCLUSIONS The expression of EphA2 can be noninvasively investigated using (99m)Tc-HYNIC-SWL by SPECT imaging. The in vitro and in vivo characteristics of (99m)Tc-HYNIC-SWL make it a promising probe for EphA2-positive tumor imaging.

An In Vitro and In Vivo Evaluation of a Reporter Gene/Probe System hERL/18F-FES

Purpose To evaluate the feasibility of a reporter gene/probe system, namely the human estrogen receptor ligand binding domain (hERL)/16α-[18F] fluoro-17β-estradiol (18F-FES), for monitoring gene and cell therapy. Methods The recombinant adenovirus vector Ad5-hERL-IRES-VEGF (Ad-EIV), carrying a reporter gene (hERL) and a therapeutic gene (vascular endothelial growth factor, VEGF165) through an internal ribosome entry site (IRES), was constructed. After transfection of Ad-EIV into bone marrow mesenchymal stem cells (Ad-EIV-MSCs), hERL and VEGF165 mRNA and protein expressions were identified using Real-Time qRT-PCR and immunofluorescence. The uptake of 18F-FES was measured in both Ad-EIV-MSCs and nontransfected MSCs after different incubation time. Micro-PET/CT images were obtained at 1 day after injection of Ad-EIV-MSCs into the left foreleg of the rat. The right foreleg was injected with nontransfected MSCs, which served as self-control. Results After transfection with Ad-EIV, the mRNA and protein expression of hERL and VEGF165 were successfully detected in MSCs, and correlated well with each other (R2 = 0.9840, P<0.05). This indicated the reporter gene could reflect the therapeutic gene indirectly. Ad-EIV-MSCs uptake of 18F-FES increased with incubation time with a peak value of 9.13%±0.33% at 150 min, which was significantly higher than that of the control group. A far higher level of radioactivity could be seen in the left foreleg on the micro-PET/CT image than in the opposite foreleg. Conclusion These preliminary in vitro and in vivo studies confirmed that hERL/18F-FES might be used as a novel reporter gene/probe system for monitoring gene and cell therapy. This imaging platform may have broad applications for basic research and clinical studies.